The forming and shaping of a wood element is often best carried out by pressing of the wood element against a rotating disk having a sanding surface. In one convenient form of such a device, the large sanding disk normally rotates in a vertical plane and a table for supporting the wood element is located about or slightly above a horizontal diameter of the sanding disk. The supporting table surface may be made adjustably pivotable about a horizontal axis. A user of the device typically faces the sanding disk and presses the wood element toward the moving sanding surface of the disk, often at a portion of the disk that would have a tendency to hold the wood element down on the table in the course of sanding portions of the wood element. A small gap is provided between the rotating surface of the disk and an immediately adjacent edge of the table surface.
As will be readily appreciated, even if suction is provided by external means to suck away the fine wood dust generated in such an operation, an air boundary layer generated adjacent the rotating surface of the sanding disk will create an air flow pattern toward the center of the disk surface and then radially outwardly thereof. Furthermore, portions of the wood sanded away by grit provided at the sanding surface of the disk may have a tendency to at least temporarily adhere to portions of the grit and this may tend to reduce the efficacy of the sanding operation. Such adhered wood particles may eventually become released from the sanding disk surface and, due to the air boundary layer flow, may also fly off radially from the disk surface at considerable speeds. As a consequence of such mechanisms, even with suction hoods provided above and below the table and to the sides of the sanding disk, as is common in much of the known prior art, there tends to be an unacceptable degree of air pollution in the workplace due to fine wood particles not promptly removed upon generation during use of the device.
As noted, there are numerous structures employed for providing a zone of suction close to a sanding surface in a mechanical sander. Some of these devices also employ compressed air jets to dislodge wood particles that tend to otherwise adhere to grit on a moving sanding surface.
One example of such a device is taught in U.S. Pat. No. 1,791,917, to Winsor, in which an endless sanding belt passed over two large generally cylindrical pulleys or rollers is applied to an upper surface of a wood board to sand the same and compressed air is provided through a plurality of holes in a pipe disposed close to the surface of the belt as it is about to pass over one of the cylindrical pulleys, with a suction hood being provided around the sanding belt as it passes over that pulley.
In another known example, per U.S. Pat. No. 4,525,955, to Cothrell et al., also relating to an endless sanding belt passed over a cylindrical guide pulley, the entire belt is enclosed within a shroud and intermittent blasts of compressed gaseous fluid, e.g., compressed air, are directed onto the surface of the belt as it traverses its orbital path. Specifically, the compressed gas is directed onto the surface of the belt within the shroud and at a point wherein the belt is wrapped around the surface of the roller or pulley which opens the grid pattern of the belt fabric slightly. As a consequence, wood particles that otherwise would tend to remain attached to the belt are dislodged and sucked away.
U.S. Pat. No. 3,646,712, to Quintana, teaches a dust-removing attachment device for a rotary disk power grinder or sander, wherein a continuous current of air is maintained over and around the grinding or sanding surface by flow of a pressurized gas through apertures located around a portion of an arc surrounding the sanding disk. The flow of pressurized air withdraws dust particles and the like and a mixture of compressed air and dust particles is sucked away at a location on a side of the disk sander opposite the pressurized air inlet apertures.
Numerous other generally similar devices are known in the relevant art. None, however, appear to be particularly satisfactory for use with large disk sanders in which a user presents a wood element to a substantially vertical surface of a large rotating sanding disk, wherein the user is not exposed to find particles released during the operation and the sanding disk surface is continuously cleaned of adhering wood particles.